posthtml-custom-elements-defouc
v1.0.6
Published
A PostHTML plugin to mitigate intrinsic FOUC of Custom Elements.
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andyogoReadme
PostHTML Custom Elements de-FOUC Plugin
Mitigate intrinsic Flash of Unstyled Content (FOUC) of Custom Elements V1, by delaying their visibility upon connection.
Before:
<html>
<body>
<custom-element>FOUC autonomous custom element</custom-element>
<div is="my-div">FOUC extended built-in element</div>
</body>
</html>After:
<html>
<body>
<custom-element style="visibility: hidden;">FOUC autonomous custom element</custom-element>
<div is="my-div" style="visibility: hidden;">FOUC extended built-in element</div>
</body>
</html>Install
Add PostHTML Custom Elements de-FOUC plugin to your build tool:
npm i posthtml posthtml-custom-elements-defouc
IMPORTANT: don't forget to use with-custom-elements-defouc higher-order-class for your Custom Element definitions.
Note: Depending at your targeted audience the CSS :defined pseudo-class may is a better solution.
Of course if you need to support any user with non-capable browsers :defined won't help you there.
You could handle all undefined custom elements FOUC just by these lines defined within your <head> section:
:not(:defined) {
display: none;
// or
visibility: hidden;
// or whatever you came up with
}Usage
This plugin comes with sane defaults, just add it to your PostHTML pipeline:
const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlCustomElementsDeFouc = require('posthtml-custom-elements-defouc');
posthtml()
.use(posthtmlCustomElementsDeFouc({ /* options */ }))
.process(html/*, options */)
.then(result => fs.writeFileSync('./after.html', result.html));Options
Optionally you can:
- limit this plugin to a specific
namespace - disable processing
autonomousCustom Elements or extendedbuiltinElements - apply your own custom
styleto mitigate FOUC - or use a CSS
classNameto mitigate FOUC
Limit namespace
Before:
<html>
<body>
<custom-element>content</custom-element>
<span is="builtin-element">content</span>
<namespace-element>content</namespace-element>
<span is="namespace-element">content</span>
</body>
</html>Add option:
const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlCustomElementsDeFouc = require('posthtml-custom-elements-defouc');
posthtml()
.use(posthtmlCustomElementsDeFouc({ namespace: 'namespace' }))
.process(html/*, options */)
.then(result => fs.writeFileSync('./after.html', result.html));After:
<html>
<body>
<custom-element>content</custom-element>
<span is="builtin-element">content</span>
<namespace-element style="visibility: hidden">content</namespace-element>
<span is="namespace-element" style="visibility: hidden">content</span>
</body>
</html>Disable autonomous
Before:
<html>
<body>
<custom-element>content</custom-element>
<span is="builtin-element">content</span>
</body>
</html>Add option:
const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlCustomElementsDeFouc = require('posthtml-custom-elements-defouc');
posthtml()
.use(posthtmlCustomElementsDeFouc({ autonomous: false }))
.process(html/*, options */)
.then(result => fs.writeFileSync('./after.html', result.html));After:
<html>
<body>
<custom-element>content</custom-element>
<span is="builtin-element" style="visibility: hidden">content</span>
</body>
</html>Disable builtin
Before:
<html>
<body>
<custom-element>content</custom-element>
<span is="builtin-element">content</span>
</body>
</html>Add option:
const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlCustomElementsDeFouc = require('posthtml-custom-elements-defouc');
posthtml()
.use(posthtmlCustomElementsDeFouc({ builtin: false }))
.process(html/*, options */)
.then(result => fs.writeFileSync('./after.html', result.html));After:
<html>
<body>
<custom-element style="visibility: hidden">content</custom-element>
<span is="builtin-element">content</span>
</body>
</html>Custom style
style can be either of type string or a style hash.
Before:
<html>
<body>
<custom-element>content</custom-element>
</body>
</html>Add option:
const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlCustomElementsDeFouc = require('posthtml-custom-elements-defouc');
posthtml()
.use(posthtmlCustomElementsDeFouc({ style: { display: 'none' } }))
.process(html/*, options */)
.then(result => fs.writeFileSync('./after.html', result.html));After:
<html>
<body>
<custom-element style="display: none">content</custom-element>
</body>
</html>Custom className
Before:
<html>
<body>
<custom-element>content</custom-element>
</body>
</html>Add option:
const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlCustomElementsDeFouc = require('posthtml-custom-elements-defouc');
posthtml()
.use(posthtmlCustomElementsDeFouc({ className: 'foo' }))
.process(html/*, options */)
.then(result => fs.writeFileSync('./after.html', result.html));After:
<html>
<body>
<custom-element class="foo">content</custom-element>
</body>
</html>Contributing
See PostHTML Guidelines and contribution guide.
License MIT
Proudly brought to you by <scale-unlimited>